The data provide details of the positions taken in the UK's 2016 referendum on EU membership by all Labour and Conservative MPs elected to the 2015-17 Parliament, including those who were elected during this parliament in by-elections. These data were sourced from statements made by MPs on their websites, in the media and on Twitter. details of the source of each MPs' position are included in the data set. It includes data on the each MP's party, their year of birth, the year in which they were first elected and their constituency. There is a small number of cases in which MPs did not disclose the positions on the UK's referendum on EU membership and these are noted in the data. The data allow for descriptions of the level of division within the Conservative and Labour parliamentary parties and provide an independent variable that could be used in other studies where referendum position is believed to affect other things.The 2016 referendum vote for Brexit is already having a significant effect on British political parties and the UK Parliament. It is reshaping the divisions within and between political parties, impacting upon the strategies adopted by parties and individual MPs, and requiring Parliament to adapt its structures and procedures as the Brexit process becomes a critical area of its activity. The proposed project brings together experts drawn from the fields of law and political science, who will work with the Industry and Parliament Trust to inform their research and ensure dialogue with policymakers and the business community. The project combines analysis of the importance of institutions (e.g. parliamentary procedures and structures), and legislative and regulatory norms with an examination of the motivations and behaviour of political parties, individual MPs and the government. These are linked because internal party divisions, cross-party alliances and the differing preferences of MPs on Brexit will affect how - and how well - Parliament scrutinises the process of leaving the EU. The purpose of this project is: (1) To enhance understanding of how the Brexit vote has affected UK party politics, including divisions within and between parties, the positions and preferences of MPs, party positions in Parliament and party competition on EU issues. We will collect and analyse data on the positions on the EU issue adopted by parties and MPs since 2010, assessing how divisions within parties are changing and whether new patterns of cross-party cooperation are emerging. (2) To develop knowledge of how Parliament has responded to Brexit in terms of its structures and procedures, and how effective this response has been. We will examine the work of the new Exiting the EU select committee, the European Scrutiny Committee and other departmental select committees, collecting data on and assessing divisions and cooperation within and across these bodies. (3) To identify those areas of policy that have been most subject to conflict between and within parties and are most likely to change once the UK has left the EU. After Brexit, the UK Parliament will exercise regulatory control over a range of policy areas (e.g. environmental protection, farming, employment rights) which have hitherto been legislated for at the EU level. Parliament will make choices about how, and under what principles it wishes to legislate. We assess the extent to which MPs seek to formulate UK versions of existing EU legislation or continue to broadly adopt EU norms and standards. Our research on whether MPs behave according to traditional party affiliations, or new cross-party alliances and intra-party disputes emerge will also help to explain what factors shape the post-Brexit legislative agenda. (4) To address the needs of key stakeholders by working with our impact partner the Industry and Parliament Trust (IPT) to: (a) better understand the interests and concerns of business and industry stakeholders regarding the Brexit process and the changes that Brexit is likely to bring to their activities; (b) foster effective dialogue between business and industry stakeholders and MPs, notably through a series of seminars and workshops; and (c) provide business and industry stakeholders with clear guidance and analysis of the role and activity of Parliament and MPs in the Brexit process. (5) To maximise user engagement and public understanding by working with the Director of the ERSC UK in a Changing Europe Programme and other projects within it to: (a) synthesise and develop research on parties, Parliament and the transfer of competences; (b) disseminate our research findings to a range of stakeholders and the general public in an easily-accessible form through a variety of forums; and (c) lay the foundations for future research on the impact of Brexit.

The data on Conservative MPs were collected manually using public statements on MPs' websites and blogs for all MPs present in the 2017-19 Parliament. Where such statements did not exist, we used MPs' Twitter feeds, Facebook pages and articles they published in local and national newspapers for information about their position. For Labour MPs a more automated approach was used with web scraping of MPs' websites, Twitter feeds and Facebook pages, followed by manual searches of local and national newspapers where the webscraping did not reveal a position. Data on MPs' constituencies, party, age and date of election were taken manually from the database of MPs on Parliament's website.